Fall risk is nearly 2.5 times greater in people with osteoarthritis (OA) compared to those without OA. However, the underlying mechanisms explaining this increased risk are unknown. This dissertation, which focused on trip-related falls, identified biomechanical risk factors that contribute to the increased fall risk of people with OA. The focus of the first experiment was to explain this increased fall risk by relating gait biomechanics to fall history in women with and without knee OA. Twice the number of women with knee OA reported having at least one trip-related fall in the previous year. This clinically meaningful difference was not related to between-group differences in minimum toe clearance, suggesting that the higher incidence of falls may not reflect an increased likelihood of unexpectedly contacting an obstacle during gait. The focus of the second experiment was to determine if the increase in trip-related fall risk of the OA group following large disturbances to dynamic stability was due to impaired recovery stepping responses. Women with and without knee OA were subjected to two types of large perturbations mimicking trips. Following both perturbations, women with knee OA displayed impaired control of the trunk evidenced by trunk kinematics previously shown to statistically discriminate fallers from non-fallers for healthy older adults. Furthermore, these kinematics have been shown to be modifiable using task-specific perturbation training. The third study evaluated if task-specific perturbation training could improve kinematics related to the recovery stepping response following large, treadmill-delivered postural perturbations requiring a step(s) to avoid falling. Recovery step kinematics of women with OA improved to the same extent as women in the control group. Collectively, the results of these experiments indicate that, in part, the increased risk of falls associated with OA is attributable to the same biomechanical variables that have been previously shown to explain falls by middle aged and older community-dwelling women without knee OA. Furthermore, the results strongly suggest that task-specific perturbation training has the potential to be an effective and efficient fall-prevention intervention for many people with knee OA.